Many metallic cans for holding beverages or other products are provided with easy-open can ends, wherein a pull tab attached to a tear strip that is defined by a score line in the can end may be pulled to provide an opening in the can end for dispensing the can's contents. Likewise, many food products are sold in metal containers that have ends designed to facilitate access to the contents without the use of can openers or the like.
By way of example, in the manufacture of an easy-open can end, a can end shell is first formed from a metal sheet product, preferably an aluminum sheet product. The can end shell is then conveyed to a conversion press. In the typical operation of a conversion press, a can end shell is introduced between an upper tool member and a lower tool member which are in the open, spaced apart position. A press ram advances the upper tool member toward the lower tool member in order to perform any of a variety of tooling operations such as rivet forming, paneling, scoring, embossing, tab securing, and final staking. After performing a tooling operation, the press ram retracts until the upper tool member and lower tool member are once again in the open, spaced apart position. The partially converted shell is transported to the next successive tooling operation until an easy-open can end is completely formed and discharged from the press. As one shell leaves a given tooling station or forming operation, another shell is introduced into or indexed into the vacated station, thus continuously repeating the entire easy-open can end manufacturing process. Conversion presses can operate at speeds that produce in excess of 500 can ends per minute per lane, with some machines having 4 lanes producing 2000 ends per minute. It has been the practice in the can end industry to continue to strive to reduce the gauge of the metal of the can end. The current practice is to use metal with a gauge of approximately 0.008 inch. While it should by readily apparent that each of the several tooling stations must be rigorously maintained within prescribed operating tolerances, of critical concern in the production of the converted end is the scoring station. The scoring station of the conversion press employs a knife edge tooling member that defines the panel opening in the face of the can end. The tooling for the scoring is subject to wear and converted can ends must be periodically examined to ensure that the score formed in the panel is within a predetermined tolerance that defines both the depth of the score line and the amount of residual metal below the score. If tolerances are not maintained, the converted end may either fail to open properly or simply fail prematurely during shipping and handling of the filled container. As can be appreciated, the very nature of can end formation requires a nearly continuous monitoring and adjustment of the output of the press in order to maintain product quality and avoid changes in residual, rivet head thickness, or rivet diameter that result in poor quality products.
U.S. Pat. No. 5,564,298, entitled "Die Tool and Press Monitor and Product Quality Analysis Apparatus and Method" to DeMeo which is assigned to the assignee of the instant invention, and is incorporated herein by reference as if fully set forth, discloses a die tool wear monitor. More particularly, this patent discloses the value of monitoring the force proximate die tooling stations that is generated during the approach of the upper ram toward the lower tooling and the withdrawal of the upper ram from the lower tooling.
It remains a goal of the conversion press industry to continue to strive toward the manufacture of can ends of both reduced diameter and reduced metal thickness in order to effect enhanced cost savings through the use of less metal in each packaged product. Likewise, it is another goal of the industry to maintain product quality at the highest rates of press operation and to minimize the loss of product due to the failure to quickly identify and compensate for normal changes in tooling height.
It is therefore an object of this invention to provide a conversion die tooling adjustment apparatus and method for maintaining product quality.
It is yet another object of this invention to provide a method and apparatus to compensate for changes in tooling height and adjust the individual tooling members during their normal cycle so that the product produced thereby is optimized.
It is yet another object of this invention to provide a method and an apparatus that reduces the need for periodic physical inspections of the converted can ends through the thermal control of tooling stations.
It is an object of this invention to establish an ideal thermal condition for a given tooling station and to provide an apparatus and method for monitoring and maintaining the thermal condition of the given tooling station throughout conversion press start-up and operation.